Microbiology 1: Bacterial properties

Question 1

Name the 3 Forms of bacteria and draw them?

Answer 1

rod=bacillus

Question 2

What is gram stain used for?

Answer 2

– Distinguishes between two different kinds of bacterial cell walls

-Stain indicates whether or not you have Gram-negative or Gram-positive bacteria.

Question 3

Describe the steps for gram staining?

Answer 3

– Bacteria are stained with a violet dye and iodine, rinsed in alcohol, and then stained with a red dye.

Question 4

What colour is a gram positive bacteria stained and why is it stained that colour?

Answer 4

Gram positive bacteria: Peptidoglycan in cell wall retains dye. High peptidoglycan = deep violet

Question 5

What colour is a gram negative bacteria stained and why is it stained that colour?

Answer 5

Dye is lost from thinner peptidoglcan The cells absorb counterstain making them appear pink

Question 6

What is the difference in the peptidoglycan of gram positive and gram negative bacteria?

Answer 6

Peptodoglycan in Gram posistive bacteria is much thicker than gram negative bacteria- hence gram positive can retain the dye

Question 7

Is this a gram positive or gram negative cell wall structure?

Answer 7

Gram positive

Question 8

Is this a gram positive or gram negative cell wall structure?

Answer 8

Gram negative

Question 9

How many membranes does gram positive have and how many membranes does gram negative bacteria have?

Answer 9

Gram negative bacteria have TWO MEMBRANES (inner and outer)

Gram positive only have ONE MEMBRANE

THIS IS THE KEY DIFFERENCE ^

Question 10

Name and describe the 3 ways bacteria survive in the host cell?

Answer 10

Prevent Fusion with Lysosomes - Salmonella, Mycobacteri and Chlamydia

Escape - Listeria and Shigella break down the vesicle and escape into the cytoplasm

Survive in Phagolysosome - Coxiella can just survive in the harsh environment inside a phagolysosome

Question 11

What are the two related multi-protein machines required for motility and invasion?

Answer 11

Flagella

Injectisome

Question 12

How does an injectisome cause salmonella to enter a host cell?

Answer 12

They polymerise actin into filaments

This ruffles the plasma membrane and bacteria get stuck in this ruffle

As the process dies down and returns to normal, the trapped bacteria is internalised

Question 13

What is the function of flagella?

Answer 13

flagella allows the propulsion of bacteria through fluids - they are filamentous structures and they rotate and are organised as a series of rods and filaments

Question 14

Name another method of invasion into a host cell?

Hint:Listeria and Shigell use this mechanism

Answer 14

It breaks out of the vacuole

It then assembles/polymerises actin at one pole of the bacterial cell

This polymerisation of actin generates force which propels the bacterium through the cytoplasm

This leads to the spread of the bacterium from one cell to another

These streams of actin are known as COMET TAILS

Listeria and Shigella can both do this

Question 15

Name the 3 main ways bacteria use to exchange gemetic material?

Answer 15

Transformation

Transduction

Conjugation

Bacteria can take up DNA from the environment giving them immense potential to adapt and overcome our immune system

Question 16

What is Transformation?

Answer 16

Question 17

What is transduction?

Answer 17

Question 18

What is conjugation?

Answer 18

Question 19

What is a PATHOGENICITY ISLAND?

Answer 19

PATHOGENICITY ISLAND = Horizontally Acquired DNA that contributed to Virulence

Question 20

What illness does Salmonella typhi cause?

Answer 20

typhoid fever

Question 21

What illness does Shigella cause?

Answer 21

dysentery

Question 22

What two illness can Neisseria cause?

Answer 22

meningitis, gonorrohea

Question 23

What illness can Streptococcus pneumoniae cause?

Answer 23

Pneumonia

Question 24

What illness is caused by Mycobacterium tuberculosis?

Answer 24

tuberculosis

Question 25

Name an extracellular bacteria?

Answer 25

Streptococcus

Question 26

Name an intracellular bacteria?

Answer 26

Mycobacterium

Question 27

Name an obligate intracellular bacteria?

obligate intracellular parasite- Intracellular parasites are microparasites that are capable of growing and reproducing inside the cells of a host. only show characteristics of life inside a cell

Answer 27

Chlamydia

Question 28

What substance is only present in gram negative bacterial cell walls?

Answer 28

LIPOPOLYSACCHARIDE (LPS)

Question 29

Where is LIPOPOLYSACCHARIDE (LPS) found on gram negative bacteria?

Which membrane?

Answer 29

Outer Membrane - composed mainly of LIPOPOLYSACCHARIDE (LPS)

Question 30

Is Escherichia coli gram positive or gram negative?

Answer 30

Gram negative

Question 31

Is Salmonella (typhimurium - food poisoning, typhi - typhoid) gram positive or gram negative?

Answer 31

Gram negative

Question 32

Is Shigella Gram positive or gram negative?

Answer 32

Gram Negative

Question 33

Is Vibrio cholerae gram negative or gram positive?

Answer 33

Gram Negative

Question 34

Is Neisseria (meningitidis- meningitis, gonorrhoeae- gonorrhea) gram positive or gram negative?

Answer 34

Gram Negative

Question 35

Is Staphylococcus aureus (skin diseases, endocarditis, bacteraemia, joint diseases, pneumonia) gram positive or gram negative?

Answer 35

Gram Positive

Question 36

Is Streptococcus pneumoniae (pneumonia, meningitis, otitis media) Gram Postive or Gram Negative?

Answer 36

Gram Positive

Question 37

Is Streptococcus pyogenes (tonsilitis, necrotizing fasciitis, bacteremia, scarlet fever) gram Positive or Gram Negative?

Answer 37

Gram Positive

Question 38

What bacterias are neither gram positive or gram negative?

Answer 38

Mycobacterium tuberculosis (TB)

Mycobacterium leprae (leprosy)

Question 39

What 5 things do bacteria have to do to be a pathogen?

Answer 39

Colonise - pili and fimbriae have formed to allow them to cling onto surfaces

Persist - ability to avoid the host defences - deal with innate immune function

Replicate - acquire nutrients needed for replication e.g. iron is limited in the body

Disseminate within cells, tissues, between organs and hosts

Cause Disease - produce toxins that kill host cells - dysregulation of host immune responses

CCPRD

Question 40

Are these bacteria intracellular or extracellular?

Staphylococcus

Streptococcus

Yersinia

Neisseria

Answer 40

Extracellular

Question 41

Are these bacteria intracellular or extracellular?

Listeria Shigella

Salmonella

Chlamydia

Coxiella

Answer 41

Intracellular

Question 42

Motility and Invasion require two related multi-protein machines:

Name these machines?

Answer 42

Flagella

Type III Secretion System

Question 43

What is a Type III secretion system?

Answer 43

Delivers virulence proteins into the host cell

IMPORTANT: bacterial virulence proteins (effectors) induce actin polymerisation, membrane ruffling and bacterial internalisation

Hence the type III secretory system is needed to deliver the effectors which allow the internalisation of the bacteria.

This needle structure is evolutionarily linked to the flagellum

Instead of making a flagellum, a bacterium can make this needle shaped structure which allows effector proteins to be injected into the host cell through translocase.

Many gram negative bacteria have this feature but NO GRAM POSITIVE BACTERIA HAVE THIS

This is a translocon which inserts into the plasma membrane of the host cell.

By making a passage into the cell, it allows effector proteins to be transferred from the bacterial cell to the host cell.

The effector proteins lead to actin polymerisation which causes the uptake of bacteria into the host cell.

This examples is Salmonella

Question 44

What feature does many gram negative bacteria have, but no gram positve bacteria have?

Answer 44

Type III Secretion System